Device for program controlling metal remelting processes

ABSTRACT

The device for program control of metal remelting processes, e.g., electric slag melting process, by controlling two parameters depending upon the time taken for the technological process to occur and upon the length of traverse of the electrode being remelted, said device comprising a transducer to convert the mechanical traversing of the electrode being remelted into the electric signal, said transducer being connected to the control unit whose output is connected to the parallel-coupled program-change units of the parameter under control, each of said units incorporating a photoelectric servo-system, a chart-drive mechanism, a chart carrying the graphic representation of the variation of the parameter under control, an output amplifier, a dial calibrated in the controlled-parameter values and electric control push-buttons of which one is connected to the control unit. The transducer converting the mechanical traversing of the electrode being remelted, into the electric signal has a contactless inductive displacement pickup and the following elements connected in series: a synchronous motor; a reduction unit; a differential with two sun wheels, two differential pinions and a pinion carrier carrier on which a metal plate is held; a magnetic clutch and another reduction unit mechanically engaged with the remelting electrode traversing mechanism; besides, the metal plates made fast on the differential pinion carrier is inserted into the gap between between the coil windings of the contactless inductive displacement pickup. The above-considered program device enables the programmed change of the parameter under control not only as a function of the coursing time of the technological process but also in response to the displacement of the electrode under remelting.

United States Patent Fain et a1.

[ June 17, 1975 1 DEVICE FOR PROGRAM CONTROLLING METAL REMELTING PROCESSES [76] Inventors: Pavel loelievich Fain, ulitsa Shamsheve, 15b, kv. 6; Vladimir Anatolievich Zimin, ulitsa Sojuza Svyazi, l3, kv. 5; A'ron Zakharovich Strashun, prospekt Engelsa, 69, kv. 55; Tamara lvanovna lsupova, ulitsa Vernosti, 34, kv. 67; Alexandr lvanovich Pankratov, prospekt Engelsa, l7, kv. 58; Georgy lvanovich Romanov, naberezhnaya reki Fontanki, 127, kv. 3, all of Leningrad, USSR.

[22] Filed: Feb. 21, 1974 [2]] Appl. No.: 444,667

[52] U.S. Cl 13/13; 13/13 [51] Int. Cl. F27d 11/10 [58] Field of Search 13/13, 12

[56] References Cited UNITED STATES PATENTS 3,375,318 3/1968 Kjolseth et al 13/13 3,431,344 3/1969 Borrebach 13/13 X 3,622,678 11/1971 Allen 13/13 3,662,075 5/1972 Sakai et a1. 13/13 Primary Examiner-R. N. Envall, Jr.

57 ABSTRACT The device for program control of metal remelting processes, e.g., electric slag melting process, by controlling two parameters depending upon the time taken for the technological process to occur and upon the length of traverse of the electrode being remelted, said device comprising a transducer to convert the mechanical traversing of the electrode being remelted into the electric signal, said transducer being connected to the control unit whose output is connected to the parallel-coupled program-change units of the parameter under control, each of said units incorporating a photoelectric servo-system, a chart-drive mechanism, a chart carrying the graphic representation of the variation of the parameter under control, an output amplifier, a dial calibrated in the controlledparameter values and electric control push-buttons of which one is connected to the control unit.

The transducer converting the mechanical traversing of the electrode being remelted, into the electric signal has a contactless inductive displacement pickup and the following elements connected in series: a synchronous motor; a reduction unit; a differential with two sun wheels, two differential pinions and a pinion carrier carrier on which a metal plate is held; a magnetic clutch and another reduction unit mechanically engaged with the remelting electrode traversing mechanism; besides, the metal plates made fast on the differential pinion carrier is inserted into the gap between between the coil windings of the contactless inductive displacement pickup.

The above-considered program device enables the programmed change of the parameter under control not only as a function of the coursing time of the technological process but also in response to the displacement of the electrode under remelting.

3 Claims, 5 Drawing Figures PATENTEDJUN 17 I975 SHEET F/EJ PATENTEDJUN 17 1915 uilillll FIELZ PATENTEDJUN 17 ms 3,890,457

saw 3 fin DEVICE FOR PROGRAM CONTROLLING METAL REMELTING PROCESSES This invention relates generally to productionprocess control systems and more specifically to de vices for program control of metal remelting processes.

The invention is applicable in the control systems of electroslag remelting furnaces or vacuum-arc remelting furnaces.

Known in the present-day practice is one prior-art device for program control of metal remelting processes by controlling at least one parameter such as melting current, remelting furnace voltage, ohmic resistance of the molten slag in a remelting furnace, or input power of the remelting furnace, versus the production process coursing time, said device comprising a program-change unit of the parameter under control, which incorporates a photoelectric servo-system, a chart-drive mechanism, a chart carrying the graphic representation of the variation of the parameter under control, an output amplifier and a dial calibrated in the controlled-parameter values.

A disadvantage inherent in said known device resides in failure to perform a programmed change of the parameter under control in response to the displacement of the electrode being remelted, and to automatically change over, in the course of control process, to the programmed change of the controlled parameter depending upon the displacement of the electrode being remelted.

Said disadvantage results in a definite restriction of the processing capacities of said program-control device under industrial application of the latter.

It is therefore an essential object of the present invention to provide a device for program control of metal melting processes which would be capable of performing not only the programmed change of the controlled parameter in dependence with the coursing time of the production process but also automatically changing over to the programmed change of the controlled parameter in response to the displacement of the electrode being remelted.

The essence of the present invention consists in that a device for program control of metal remelting processes by controlling at least one parameter such as remelting current, voltage of an electroslag remelting furnace, ohmic resistance of the molten slag in such a furnace, or input power of said furnace, versus the production process coursing time, comprises a programchange unit of the controlled paramater, said unit incorporating a chart-drive mechanism, a photoelectirc servosystem, a chart carrying graphic representation of the variation of the controlled parameter, an output amplifier and a dial calibrated in the controlledparameter values, the chart-drive mechanism comprising a synchronous motor and chart traction rings mechanically associated with the synchronous motor, whereas the photoelectric servo-system comprises a power amplifier, a carriage with illumination lamp and a photoresistor connected to the power amplifier input, an induction motor connected to the power amplifier output and mechanically associated with the carriage, and a slidewire arranged over the chart-drive mechanism in parallel with the chart surface and connected to the output amplifier, the slider of said slidewire being mechanically coupled with the carriage, according to the invention incorporates also a transducer to convert mechanical displacement of the electrode being remelted into the electric signal, said transducer comprising a contactless inductive displacement pickup and the following elements connected in series: a synchronous motor, a reduction unit, a differential with two sun wheels, two differential pinions and a pinion carrier on which a metal plate is secured, a magnet clutch and another reduction unit which is mechanically associated with the remelting electrode traversing mechanism, said metal plate being inserted into the gap between the coil windings of the contactless inductive displacement pickup which is connected to the input of the control unit whose outputs are connected to the synchronous motor and to the magnetic clutch of the transducer of mechanical displacement of the remelting electrode into the electric signal, as well as to the synchronous motor of the chart-drive mechanism of the controlled-parameter program-change unit.

The device can incorporate another controlled parameter program-change unit similar to the former one and connected to the control unit output in parallel with the first controlled-parameter program-change unit, each of said units being adapted to control at least one parameter in the capacity of which may be melting current, the voltage of an electroslag remelting furnace, ohmic resistance of the molten slag in such a furnace, or input power of said furnace, so as to provide a possibility to control two parameters at a time.

It is expedient that each program-change unit of the controlled parameter have electric control buttons one of which be connected to the control unit to effect transfer from a programmed change of the controlled parameters depending upon the coursing time of the production process to such a change of said parameters in response to the displacement of the electrode under remelting.

The possibility of a programmed change of the controlled parameters depending upon the coursing time of the production process and upon the displacement of the electrode being remelted by resorting to the aforedescribed device results in a more stable furnace operating conditions, better metal refinement and ingot surface, more successful elimination of shrinkage cavities and, hence, higher yield of good metal.

In what follows the invention is illustrated in an exemplary embodiment thereof to be read in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates the functional diagram of a device for program control of metal remelting processes, according to the invention;

FIG. 2 illustrates the functional electric diagram of a device for program control of metal remelting processes, according to the invention;

FIG. 3 illustrates a schematic circuit diagram of a power amplifier of a controlled-parameter programmed-change unit;

FIG. 4 illustrates a schematic circuit diagram of an output amplifier of a controlled-parameter programmed-change unit; and

FIG. 5 illustrates a schematic circuit diagram of a control unit thyristor-based amplifier.

Reference being now directed to the accompanying drawings, the device for program control of the processes of electric slag metal remelting comprises a transducer 1 (FIG. 1) to convert the mechanical displacement of the electrode being remelted into the electric signal, said transducer incorporating a contactless inductive displacement pickup 2 and seriesconnected: a synchronous electric motor 3, a reduction unit 4, a differential 5, a magnetic clutch 6 and another reduction unit 7, the latter being connected to a mechanism 8 for displacing an electrode 9 under remelting.

The device has also a control unit 10 to whose input is connected the contactless inductive displacement pickup 2, while to the respective outputs thereof are connected parallel-coupled units 11 and 12 of programmed change of the controlled parameter, the synchronous motor 3 and the magnetic clutch 6 of the transducer 1 for converting mechanical displacement of the electrode 9 being remelted into the electric signal. The output of the units 11 and 12 are connected to an electric slag remelting furnace 13.

Each of the units 11 (FIG. 2) and 12 comprises a chart-drive mechanism which incorporates a synchronous electric motor 14, chart-traction rings 15, 15 me chanically coupled therewith and a chart 16 carrying graphic respresentations A and B for the units 11 and 12, respectively, where A represents the furnace remelting current variation and B represents the voltage variation of the electroslag remelting furnace; besides, used as the controlled parameters may be also the ohmic resistance of the molten slag in an electroslag remelting furnace, or input power of such a furnace.

The chart-drive mechanism of each of the units 11 and 12 feeds the chart 16 carrying the graphic representation A for the unit 11 and the representation B for the unit 12, both representations being converted into the electrical signal by the photoelectric servosystem incorporated into each of the units 11 and 12.

The photoelectric servosystem has a power amplifier 17, a carriage 18 with an illumination lamp 19 fed on an A.C. source (not shown in the drawing) and a photoresistor 20 connected to the input of the power amplifier 17, an induction motor 21 connected to the output of the power amplifier 17 and mechanically associated with the carriage 18, and a slidewire 22, an end 23 of one arm of said slidewire and a slider 24 thereof being connected to an output amplifier, while the slider 24 of the sildewire 22 is mechanically coupled with the carriage 18. The slidewire 22 is arranged over the chart-drive mechanism in parallel with the surface of the chart 16.

Each of the units 11 and 12 of the programmed change of the controlled parameter comprises also a dial 26 of the controlled parameter values calibrated in percent from 0 to 100.

According to the invention, each of the units 11 and 12 has an electric control button 27 traversable along the dial 26 and adapted to be locked in position against the division of the scale 16 corresponding to the preselected point on the graphic representation (curve) A for the unit 11 and on the curve B for the unit 12.

The electric control button 27 of each of the units 11 and 12 is so positioned that the carriage 18, while traversing in keeping with the curve A for the unit 11 and with the curve B for the unit 12 exerts mechanically thereupon.

The electric control button 27 of the unit 11 with its terminal connected to the power source not shown in the drawing, is coupled to triggers 28 and 29 of the control unit 10, while the other terminal of said electric button is fed with the DC. negative voltage from said power source not shown in the drawing. The control unit 10 comprises also a thyristor amplifier 30 connected to the trigger 28 via a transistor amplifier 31, and a thyristor amplifier 32 connected to the trigger 29 through an inverter 33, the output of the contactless inductive displacement pickup 2 being connected to the thyristor amplifier 32 through inverters 34 and 35.

The output of the thyristor amplifier 32 of the control unit 10 is connected to the parallel-coupled synchronous motors 14 of the chart-drive mechanisms of the unit 11 and 12 for the programmed change of the controlled parameter and to the synchronous motor 3 of the transducer 1 for converting mechanical displacement of the electrode being remelted into the electric signal.

The output of the thyristor amplifier 30 of the control unit 10 is connected to the magnetic clutch 6 of the transducer 1, said clutch being engaged with a sun wheel 36 of the differential 5.

The differential 5 of the transducer 1 has another sun wheel 37 which is engaged through the reduction unit 4 with the synchronous motor 3, differential pinions 38 and 39 and a pinion carrier 40 on which is secured a metal plate 41 inserted into a gap 42 in between coil windings 43 of the contactless inductive displacement pickup 2.

The power amplifier 17 (FIG. 3) comprises a transformer 44 having a primary 45 interconnected with a primary 46, and secondaries 47 and 48.

Connected to the joint point of the primaries 45 and 46 is one of the output leads of a ballast resistor 49 whose other output lead is connected to a terminal 50.

A tap 50 of the primary 46 of the transformer 44 is connected to one of the output leads of a resistor 51 whose other output lead is connected to terminals 52 and 53. A tap 53' of the primary 45 of the transformer 44 is connected to a terminal 54.

The secondary 47 of the transformer 44 with its one tap 55 is connected to the base of a transistor 56 into the emitter circuit of which is connected with its one output lead a resistor 57 whose other output lead is connected to a thermostabilizing diode 58. The other tap 58' of the secondary 47 of the transformer 44 is connected to a resistor 59 and to the thermostabilizing diode 58. The resistor 59 is connected to the collector of the transistor 56 and to diodes 60 and 61.

The secondary 48 of the transformer 44 with its one tap 61' is connected to the base of a transistor 62 whose emitter is connected through a resistor 63 and a thermostabilizing diode 64 to the other tap 64' of the secondary 48 of the transformer 44 and to a resistor 65 which is connected to the collector of the transistor 62, a resistor 57 and a terminal 66. The resistor 63 is connected also through diodes 67, 68 to secondaries 69, of a transformer 71. The secondaries 69 and 70 of the transformer 71 are interconnected and the joint-tap is brought to a terminal 72. A tap 72 of the secondary 69 is connected to the diodes 67, 60, while a tap 72" of the secondary 70 is connected to the diodes 61, 68. A primary 73 has terminals 74 and 75.

Now let us consider the output amplifier 25 (FIG. 4) in detail. An input terminal 75' of the output amplifier 25 is connected to the positive connection lead of capacitor 76 and, through a resistor 77, to the collector of a transistor 78 and to one of the connection leads of an isolating capacitor 79.

The negative connection lead of the capacitor 76 is coupled to an input terminal 80, an output terminal 81 and, through a resistor 82 inserted in the negative current feedback thereof, to a positive supply busbar 83.

The other connection lead of the isolating capacitor 79 is coupled to resistors 84, 85 which establish a voltage divider, and to the base of a transistor 86 whose emitter is connected to parallel-coupled a resistor 87 and a capacitor 88. A voltage stabilizing tube (stabilitron) 89 is connected in parallel with the voltage divider built round the resistors 84, 85. The resistor 84 is connected via a capacitor 90 to the collector of the transistor 86 and, through resistors 91, 92, to a negative supply terminal 93.

The resistor 85 is connected to the positive supply busbar 83.

A primary 94 of a transformer 95 is connected in par allel with the capacitor 90 to form an oscillating circuit therewith.

A positive feedback secondary 96 of the transformer 95 is connected with its one end to a resistor 97 and with the other end, to the collector of the transistor 78.

A secondary 98 of the transformer 95 is connected with its tap 98' to a resistor 99, a resistor 100, to the base of a transistor 101 and, through a voltage stabilizing tube (stabilitron) 102, to the positive supply busbar 83.

The resistors 99 and 100 establish a voltage divider between the positive supply busbar 83 and the negative voltage fed from the terminal 93 through the resistor 92.

The other tap 102 of the secondary 98 is connected through a capacitor 103 to a resistor 104, a capacitor 105 and a voltage stabilizing tube (stabilitron) 106. The capacitor 105 is connected in parallel with the resistor 104 to the positive supply busbar 83. The stabilitron 106 is inserted in the emitter circuit of the transistor 101 whose collector is connected, through a capacitor 107 and a primary 108 of a transformer 109 connected in parallel to form an oscillating circuit, to the joint point of the resistors 99, 92 and 91. The transformer 109 has a secondary 110 with a central tap which is connected to the terminal 93 and, through a capacitor 111, to a terminal 112.

Taps 112' and 112" of the secondary 110 of the transformer 109 are connected, through respective diodes 113 and 114, to each other, to one of the output leads of a resistor 115 and to the base of a transistor 116, while the other output lead of the resistor 115 is connected to the terminal 93. The emitter of the transistor 116 is connected, through a resistor 117, to the terminal 93. The collector of the transistor 116 is connected to an output terminal 118 and to the negative output lead of a capacitor 119, while the positive output lead of the capacitor 119 is connected to the terminal 112.

The load of the output amplifier 25 in the capacity of which use is made of the electric slag melting furnace 13 (FIG. 2), is connected to the terminals 81 and 118.

The thyristor amplifier 30 (FIG. 5) and the thyristor amplifier 32 similar thereto, comprise a terminal 120 to which diodes 121 and 122 are connected, the diode 121 being connected to a terminal 123 through a diode 124, while the diode 122 is connected to the terminal 123 through a diode 125. A thyristor 126 is connected to the joint point of the diodes 121 and 124 with one of its output leads, while the other output lead the thyristor is connected to the joint point of the diodes 122 and 125 and to a terminal 127. The control output lead of the thyristor 126 is connected to a terminal 128. The amplifier 30 comprises also terminals 129 and 130.

Let us consider the operation of the device for program control of metal remelting processes from the instance where the furnace operator sets and clamps the electric control button 27 of the unit 11 against the appropriately selected value of the curve A, i.e., furnace remelting current variation, whereupon the device is connected to the power mains so that mains voltage is impressed upon the power unit, the synchronous motor 14 and the induction motor 21 of each of the units 11 and 12, as well as upon the synchronous motor 3 of the transducer 1 (the mains terminals, delivery of the mains voltage to the afore-mentioned consumers, as well as the power unit of each of the units 11 and 12 are not shown in the drawing).

From the power supply unit of each of the units 11 and 12 voltage is fed to the illumination lamp 19 of the carriage 18 of the photoelectric servosystem, to the power amplifier 17, the slidewire 22 and the output amplifier 25. All the elements of the unit 10 are fed from a DC. and AC. supply source which is not shown in the drawing.

Once the supply voltage has been fed, a signal is delivered from the output of the trigger 28 of the control unit 10 to the input of the inverter 35 which remains enabled till the variation in the state of the trigger 28, whereas no signal arrives from the output of the trigger at the inverter 33 connected thereto, said inverter remaining disabled and a signal is applied from the output thereof to the thyristor amplifier 32 whose output signal sets in rotation the synchronous motor 3 and the synchronous motors 14 of each unit 11 and 12.

No signal is fed to the transistor amplifier 31 from the trigger 28 which, in turn, does not enable the thyristor amplifier 30 and the latter therefore feeds no voltage to the magnetic clutch 6 which occurs to be disaengaged.

The motor 3 imparts rotation, through the reduction unit 4, to the sun wheel 37 of the differential 5, said sun wheel transmitting rotation to the pinions 38, 39 and therefrom to the sun wheel 36; since the latter rotates freely round its own axis due to the magnet clutch 6 being disengaged, the pinion carrier 40 with the metal plate 41 fixed thereon remains immobile.

Simultaneously the chart-drive mechanism of each unit 11 and 12 draws at a constant speed the chart 16 carrying the curve A for the unit 1 l and the curve B for the unit 12 which chart, while traversing under the photoresistor 20 of the carriage 18 of the photoelectric servosystem, causes the carriage 18 of each unit 1 1 and 12 to move in accordance with the curve A for the unit 11 and the curve B for the unit 12. Accordingly moves the slider 24 of the slidewire 22 which slider is mechanically coupled to the carriage 18, thus translating the varying signal to the input of the output amplifier 25 with the result that an electric pulse appears at the output said amplifier 25 of each units 1 1 and 12, said pulse corresponding to the curve A, Le, remelting current variation, for the unit 11 and to the curve L, i.e., furnace voltage variation, for the unit 12, both variations being referenced to the production process duration time. The output signals from the units 11 and 12 are sent to the electric slag melting furnace 13.

As the chart 16 is moved A thereon reaches its value preset by the operator, at which the carriage 18 with the illumination lamp 19 and the photoresistor 20 exerts mechanically upon the electric control button 27 which, upon getting closed, effects change over from the programmed variation of the remelting current and of the electroslag remeltin g furnace voltage as the function of the production process duration time to the programmed variation of said parameters as the function of the displacement of the electrode being remelted, said changeover occurring by virtue of a signal impressed upon the inputs of the triggers 28 and 29 to cause both to flip; as a result, the inverter 33 gets enabled so that no enabling signal is sent from the output thereof to the thyristor amplifier 32, whereas the transistor amplifier 31 enables the tyristor amplifier 30 whose output signal is fed to energize the magnetic clutch 6 which gets engaged to rigidly couple the sun wheel 36 of the differential with the reduction unit 7 mechanically associated with the mechanism 8 for displacing the electrode 9 being remelted.

Further on, displacement of the electrode 9 under remelting is transmitted through the reduction unit 7, the magnetic clutch 6, the sun wheel 36 of the differential 5 to the pinion carrier 40 with the metal plate 41 secured thereon which plate, while moving, comes out from the gap 42 between the coil windings 43 of the contactless inductive displacement pickup 2 for a length large enough for a relaying pulse to appear at the output thereof which pulse upon passing through the inverters 34 and 35 of the control unit 10 enables the thyristor amplifier 32, the signal from the output thereof making rotate the synchronous motor 3 and, concurrently, the synchronous motor 14 of each of the units 11 and 12.

The synchronous motor 3 imparts reverse rotation, through the reduction unit 4, to the sun wheel 36 and the pinion carrier 40 of the differential 5, together with the metal plate 41 made fast on said carrier, which plate, while moving, enters the gap 42 between the coil windings 43 of the contactless inductive displacement pickup 2 until the relaying pulse disappears from the output thereof which pulse, upon being transmitted through the inverters 34 and 35 and the thyristor amplifier 32 to the synchronous motor 3 of the transducer 1 and to the synchronous motor 14 of each unit 11 and 12, causes said motors to rotate.

As a result the thyristor amplifier 32 gets disabled and the synchronous motor 3 of the transducer 1 and the synchronous motor 14 of each unit 11 and 12 get at standstill until the displacement of the electrode 9 under remelting transmitted from the mechanism 8 through the reduction unit 7, the magnetic clutch 6, the sun wheel 36 and the pinion carrier 40 to the metal plate 41 causes the latter to come out again from the gap 42 between the coil windings 43 of the contactless inductive displacement pickup 2 with the result that a relaying pulse appears again at the output thereof which is applied through the inverters 34 and 35 to the thyristor amplifier 32 to cause it to deliver a signal to restart the synchronous motor 3 and the synchronous motor 14 of each if the units 11 and 12. As the electrode 9 under remelting performs further motion the aforestated process is recycled repeatedly.

Thus, the chart-drive mechanism of each of the units 11 and 12 draws the chart 16 carrying the curve A of the remelting current variation, for the unit 11 and the curve B of the furnace voltage variation, for the unit 12, in dependence with and proportionate to the length of displacement of the electrode 9 being remelted.

Now let us consider a more detailed functional analysis of the power amplifier 17.

When the device for program control of metal remelting processes is energized from power mains, mains voltage is fed to the terminals 50, 52 (FIG. 3) and to the terminals 74, 75 of the power amplifier 17 so that part of the photoresistor 20 (FIG. 2) which is connected to the terminals 53, 54 (FIG. 3) is exposed to light with the result that the bridge constituted by the photoresistor 20 (FIG. 2) the resistor 51 (FIG. 3) and the primaries 45 and 46 of the transformer 44 is in the balanced state. As the chart 16 (FIG. 2) moves, the illumination of the photoresistor 20 changes accordingly and, depending upon whether the magnitude of the photoresistor 20 is decreased or increased, an A.C. voltage of the corresponding phase appears across the secondaries 47 (FIG. 3) and 48 of the transformer 44.

Since the secondaries 47, 48 are connected in phase opposition, during the first half-wave impressed upon the base of the transistor 56 is a negative voltage and upon the base of the transistor 62, a positive voltage, the transistor 56 gets enabled to pass the current from the joint point of the secondaries 69, through the load connected to the terminals 72, 66, via the resistor 57, the transistor 56 and one of the diodes 60, 61 to one of the secondaries 69, 70 of the transformer 71.

As the load of the power amplifier 17 (FIG. 2) use is made of the control winding of the induction motor 21, said winding being not shown in the drawing.

During the second half-wave a positive voltage is applied to the base of the transistor 56 (FIG. 3) and a negative voltage is applied to the base of the transistor 62 with the result that current is passed through one of the diodes 67, 68, the transistor 62, via the aforesaid load to the joint point of the secondaries 69, 70.

Thus, an alternating current flows through said load in the phase depending upon the illumination of the photoresistor 20 (FIG. 2).

Since the power amplifier 17 has as its load the control winding of the inductor motor 21 mechanically coupled to the carriage l8 and the photoresistor 20, this ensures traversing of the carriage 18 with the photoresistor 20 under the dark strip applied to either of the graphic representation A and B, in such a direction as to bring the bridge constituted by the primaries 45, 46 of the transformer 44, the resistor 51 and the photoresistor 20 (FIG. 2), in the state of balance.

Now let us proceed to a detailed functional analysis of the output amplifier 25 (FIG. 4).

Upon energizing the device discussed herein, a positive voltage is applied to the terminals 93 and 1 12 from a DC. power source which is not shown in the drawing.

The signal from the slidewire 22 (FIG. 2) is delivered to the input terminals (FIG. 4) of the amplifier 25, passed through the resistor 77 and the capacitor 79 and impressed upon the base of the transistor 86, thus causing a voltage variation across the primary 94 of the transformer 95 which primary winding serves as the collector load of the transistor 86.

The variation of the voltage across the primary 94 is transformed into the positive feedback secondary 96. The signal from said secondary 96 acts upon the transistor 78 which, due to an instantaneous transmission coefficient, still more amplifies the input signal. Hence, part of the circuitry incorporating the transistors 78 and 86, the resistors 97, 84, and 87, the capacitors 9 79, 88, 90, the stabilitron 89 and the transformer 95, starts operating in a self-oscillating mode.

From the secondary 98 of the transformer 95 the signal arrives at the base of the transistor 101. Part of the circuitry incorporating the transistor 101, the stabilitrons 102 and 106, the resistors 99, 100, 104, the capacitors 103, 105, 107 and the transformer 109 with the primary 108 and the secondary 110, is in fact a tuned amplifier which still more multiplies the signal fed from the part of the circuitry operating in a selfoscillating mode.

The signal picked up from the secondary 110, is rectified by the diodes 113, 114 and arrives as a DC. voltage at the base of the transistor 116 which together with the resistors 115 and 117 forms the output amplification stage.

With the load connected across the terminals 81 and 118, current is free to pass through the resistor 82, said load, the collector and emitter of the transistor 116 and the resistor 117.

When current flows through the load and the resistor 82, voltage drop across the resistor 82 is direct proportion to the magnitude of the current passing through the collector of the transistor 116 and is compared with the magnitude of the input signal, whereby a linear dependence of the variation of the magnitude of the signal at the input of the amplifier 25 is attained.

Let us consider the operation of the thyristor amplifier 30 (FIG. and the thyristor amplifier 32.

When the device for program control of metal remelting processes is energized, the aforesaid A.C. voltage is fed across the terminals 120 and 129.

Then the load is connected across the terminals 123, 130 in the capacity of which, say, the synchronous motor 3 (FIG. 2) is used.

Applied to the terminal 127 (FIG. 3) is a negative voltage from the DC source which also feeds the control unit 10, said source, as it has been stated above, being not shown in the drawing.

When no positive voltage is applied to the terminal 128 with respect to the voltage applied to the terminal 127, fed, say, from the inverter 33 (FIG. 2), the thyristor 126 (FIG. 5) is disabled and no A. voltage is fed across the terminals 123, 130; conversely, when the thyristor gets conductive in response to a positive enabling signal fed to the terminal 128, the negative halfwave of the A.C. voltage is passed through the diode 122, the thyristor 126 and the diode 124 and impressed upon the load, while the positive half-wave of the A.C. voltage is impressed upon the load after having passed through the diode 121 the thyristor 126 and the diode 125.

The afore-discussed device for program control of metal remelting processes is capable of such a contrl procedure that is characterized by the programmed variation of the controlled parameters not only referenced to the production process duration time but also in response to the displacement of the electrode 9 being remelted.

What is claimed is:

1. A device for program control of metal remelting processes in an electroslag remelting furnace having an electrode for remelting, and a mechanism for displacing said electrode, by controlling at least one parameter based upon, respectively, the remelting current, the voltage of the electroslag remelting furnace, the ohmic resistance of the molten slag in said electroslag remelting furnace, and the power released in the electroslag remelting furnace depending on the duration of the remelting process and the position of said electrode in the electroslag remelting furnace, said electorde being connected to said mechanism for displacing said electrode in the electroslag remelting furnace, comprising:

a. two units for effecting programmed changes in the parameter being controlled;

b. a converter for converting the displacement of said electrode into an electric signal; and

c. a control unit for operating said units for the programmed changes in the parameter being controlled in dependence upon signals received from said converter.

2. A device for program control as claimed in claim 1, said converter comprising:

a. a differential having two sun wheels, two differential pinions and a pinion carrier;

b. a metal plate attached to said pinion carrier;

c. a reduction unit having a electromagnetic clutch for transmitting rotation from the mechanism for displacing the electrode to a first one of the sun wheels of the differential upon the electromagnetic clutch being energized with supply voltage from the control unit;

(1. a synchronous motor including a reduction unit for rotating the other sun wheel of the differential upon the synchronous motor being supplied with a signal from the control unit; and

e. a contactless inductive pickup having windings with a gap provided therebetween, and a metal plate located in said gap for transmitting a signal to the control unit when the plate leaves the gap in response to the rotation of the mechanism for displacing the electrode and returning into the gap when a signal is applied to the synchronous motor from the control unit.

3. A device as claimed in claim 1, wherein each said unit for programmed change of the controlled parameter has an electric control button; one of said electric control buttons is connected to said control unit so as to change over from the programmed change of the controlled parameter against the time of duration of the production process to the programmed change of said controlled parameter in response to the displacement of said electrode being remelted. 

1. A device for program control of metal remelting processes in an electroslag remelting furnace having an electrode for remelting, and a mechanism for displacing said electrode, by controlling at least one parameter based upon, respectively, the remelting current, the voltage of the electroslag remelting furnace, the ohmic resistance of the molten slag in said electroslag remelting furnace, and the power released in the electroslag remelting furnace depending on the duration of the remelting process and the position of said electrode in the electroslag remelting furnace, said electorde being connected to said mechanism for displacing said electrode in the electroslag remelting furnace, comprising: a. two units for effecting programmed changes in the parameter being controlled; b. a converter for converting the displacement of said electrode into an electric signal; and c. a control unit for operating said units for the programmed changes in the parameter being controlled in dependence upon signals received from said converter.
 2. A device for program control as claimed in claim 1, said converter comprising: a. a differential having two sun wheels, two differential pinions and a pinion carrier; b. a metal plate attached to said pinion carrier; c. a reduction unit having a electromagnetic clutch for transmitting rotation from the mechanism for displacing the electrode to a first one of the sun wheels of the differential upon the electromagnetic clutch being energized with supply voltage from the control unit; d. a synchronous motor including a reduction unit for rotating the other sun wheel of the differential upon the synchronous motor being supplied with a signal from the control unit; and e. a contactless inductive pickup having windings with a gap provided therebetween, and a metal plate located in said gap for transmitting a signal to the control unit when the plate leaves the gap in response to the rotation of the mechanism for displacing the electrode and returning into the gap when a signal is applied to the synchronous motor from the control unit.
 3. A device as claimed in claim 1, wherein each said unit for programmed change of the controlled parameter has an electric control button; one of said electric control buttons is connected to said control unit so as to change over from the programmed change of the controlled parameter against the time of duration of the production process to the programmed change of said controlled parameter in response to the displacement of said electrode being remelted. 